1. Field of the Invention
The invention relates to twin flow turbo jet engines.
2. Summary of the Prior Art
The increase in the cost of fuel has encouraged engine manufacturers to improve the efficiency of engines and with this in mind to eliminate defects which hitherto appeared to be of secondary importance.
Their attention has thus been drawn to small deformations arising in the primary zone of the engine and resulting from loadings which cause flexing. These flexing movements can result in an increase in the clearance at the blade tips and thereby reduction in the efficiency of the engine.
As a result of the shape of the engine in the form of a wasp's body, the only reinforcement of the casing had no other result than an increase in the weight, without leading to the anticipated result. One solution of this problem was described in the article "Structural load carrying engine cowls" by K. W. Porter appearing at pages 54 and 55 of the October 1981 issue of the Journal "Astronautics and Aeronautics". The engine casing surrounding the engine is supported at the front in an annular member secured to the fan casing and at the rear within an annular support. The annular support and the ring are directly or indirectly supported by the strut or pylon of the associated aircraft.
The structural cowling is formed by two semi-cylindrical half-cowlings comprising radial limbs and longitudinal cross members.
The forward edges of the half-cowling are provided with a radial tongue of V section, directed towards the centre. The forward annular member has an annular groove of complementary profile to that of the tongue.
The rear edges of the half-cowling have a profile provided for adaption to the periphery of the rear annular support. The half-cowlings are pivoted at their upper longitudinal edges to a plate of the structure and are connected by hydraulic actuators which enable, when locking means, disposed on the lower longitudinal edges of the half-cowlings, are closed, to apply a tension force on the two half-cowlings and to ensure a positive locking on the forward and rear securing means. A cowling of high rigidity is thus provided which accommodates the forces to which the casing is subjected.
Although the structural cowling such as has been described has enabled a substantial reduction in the mechanical deformation of the casing, it is not the same for the deformation resultant from temperature changes. In practice, the temperatures longitudinally of the casing are very different from those taken up by the cowling and, as a result of the longitudinal flanging of the casing, the longitudinal deformation although of small amplitude nevertheless produces substantial forces which limit the efficacy of the cowling assembly.
The invention has as its object a structural cowling of a type similar to that hereinbefore described but comprising means for overcoming disadvantages resulting from thermal expansion of the engine, whilst ensuring aerodynamic continuity of the flow and fluidtightness while at the same time permitting ready access to the engine thus equipped and responsive to the stresses of a thrust reverser of the fan.